U.S. patent number 5,344,492 [Application Number 08/089,526] was granted by the patent office on 1994-09-06 for vapor growth apparatus for semiconductor devices.
This patent grant is currently assigned to Kabushiki Kaisha Toshiba. Invention is credited to Mitsuo Sato, Yuusuke Sato, Kiyoshi Yoshikawa.
United States Patent |
5,344,492 |
Sato , et al. |
September 6, 1994 |
Vapor growth apparatus for semiconductor devices
Abstract
A vapor growth apparatus has a susceptor which rotates in a
water cooled reaction tube with holding semiconductor susbstrates
thereon. A heater is provided in order to heat the susceptor and to
maintain a predetermined temperature. This heater is comprised of
an inner heater, which heats the inner part of the susceptor, and a
peripheral heater, which heats the peripheral part of the
susceptor. The peripheral heater is made thicker than the inner
heater. In addition, these inner and peripheral heaters are
connected in parallel with each other. So, the peripheral heater
can generate more heat than the inner heater so as to compensate
the temperature decrease in the peripheral part of the susceptor,
without loosing the mechanical strength of the whole heater.
Inventors: |
Sato; Mitsuo (Zama,
JP), Yoshikawa; Kiyoshi (Kawasaki, JP),
Sato; Yuusuke (Tokyo, JP) |
Assignee: |
Kabushiki Kaisha Toshiba
(Kawasaki, JP)
|
Family
ID: |
16368747 |
Appl.
No.: |
08/089,526 |
Filed: |
July 21, 1993 |
Foreign Application Priority Data
|
|
|
|
|
Jul 23, 1992 [JP] |
|
|
4-197101 |
|
Current U.S.
Class: |
118/725; 118/724;
118/730 |
Current CPC
Class: |
C23C
16/4586 (20130101); C23C 16/46 (20130101) |
Current International
Class: |
C23C
16/458 (20060101); C23C 16/46 (20060101); C23C
016/00 () |
Field of
Search: |
;118/725,724,730 |
Foreign Patent Documents
|
|
|
|
|
|
|
59-44819 |
|
Mar 1984 |
|
JP |
|
2-262331 |
|
Oct 1990 |
|
JP |
|
3235325 |
|
Oct 1991 |
|
JP |
|
Primary Examiner: Bueker; Richard
Attorney, Agent or Firm: Foley & Lardner
Claims
What is claimed is:
1. A vapor growth apparatus for semiconductor devices,
comprising:
a susceptor which rotates in a water cooled reaction room while
holding semiconductor substrates thereon; and
a heater for heating said susceptor;
wherein said heater comprises an inner and a peripheral heater
electrically connected in parallel with each other.
2. The vapor growth apparatus as claimed in claim 1, wherein the
temperature of said peripheral heater rises higher than that of
said inner heater.
3. The vapor growth apparatus as claimed in claim 1, wherein the
total resistance value of said peripheral heater is lower than that
of said inner heater.
4. The vapor growth apparatus as claimed in claim 1, wherein said
peripheral heater is thicker than said inner heater.
5. The vapor growth apparatus as claimed in claim 1, wherein the
cross-sectional area of said peripheral heater is larger than that
of said inner heater.
6. The vapor growth apparatus as claimed in claim 1, wherein said
peripheral heater is comprised of an outer circle and two inner
semi-circles, which are electrically connected so as to compose a
series-parallel circuit.
7. The vapor growth apparatus as claimed in claim 1, wherein both
ends of said inner and peripheral heaters are fixed to current
supply terminals respectively through connecting blocks which are
fixed to each end of said heaters.
8. A vapor growth apparatus for semiconductor devices,
comprising:
a susceptor which rotates in a water cooled reaction room with
holding semiconductor wafers thereon;
a first heater for heating the inner part of said susceptor;
and
a second heater for heating the peripheral part of said
susceptor,
said second heater having the total resistance value lower than
that of said first heater.
9. The vapor growth apparatus as claimed in claim 8, wherein said
second heater is further comprised of an outer circle and two inner
semi-circles, which are connected to compose a series-parallel
circuit.
10. The vapor growth apparatus as claimed in claim 8, wherein said
second heater is thicker than said first heater.
11. A vapor growth apparatus for semiconductor devices,
comprising:
a susceptor which rotates in a water cooled reaction room while
holding semiconductor substrates thereon;
a heater for heating said susceptor; and
a pair of current supply terminals for supplying said heater with
electric current;
wherein said heater comprises an inner and a peripheral heater
electrically connected in parallel to each other.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a vapor growth apparatus for
semiconductor devices, such as compound semiconductor devices. In
particular, this invention relates to a vapor growth apparatus for
growing thin films from vapor phase by the MOCVD (Metal Organic
Chemical Vapor Deposition) method in which a water cooled reaction
tube of the vertical type is used.
2. Description of the Prior Arts
The cross-sectional view of a conventional vapor growth apparatus
for semiconductor devices is shown in FIG. 6a. This apparatus has a
water cooled reaction tube of the vertical type. As shown in FIG.
6b a plurality of semiconductor wafers (substrates) 21 are placed
on a susceptor 1 which is in a disk-like form. These wafers 21 are
then subjected to the MOCVD method in order to grow thin films on
their surfaces.
FIG. 7 is a cross-sectional view showing the structure of the
susceptor part contained in the prior art vapor growth apparatus
mentioned above. FIGS. 8a, 8b, and 8c are the side view, the plan
view, and the cross-sectional view of an integral type heater 102
used in the apparatus.
As shown in FIGS. 7 and 8, integral type heater 102 used in the
prior art apparatus is installed in susceptor receiver 11 and
connected with current supply terminals 8a and 8b.
Also, as shown in FIG. 6a, the reaction room contained in the
apparatus has a shape such as that of a cone, in order to make
reaction gas flow most suitable and to obtain the most suitable
concentration gradient of the reaction gas. Accordingly, susceptor
1 is close to the lower part of the reaction room, the part which
is wider than the upper part. Further, the reaction room is cooled
by water so as to prevent the adhesion of products, which are
generated by reaction, onto the inner wall. As a result, the
thermal radiation from susceptor 1 is relatively large in this
apparatus.
In addition, susceptor receiver 11 is placed around susceptor 1
such that receiver 11 holds susceptor 1 from its periphery. This
susceptor receiver 11 is integrated into a rotator. Therefore, heat
is released due to the thermal conduction from the peripheral part
of susceptor 1 to receiver 11.
Moreover, the temperature of the peripheral part of susceptor 1
largely decreases due to the gas flow during a process of vapor
growth. As a result, wafer characteristics of products, especially
on the peripheral part of susceptor, become inhomogeneous. For
example, in producing semiconductor lasers with this apparatus, the
wavelength distribution of semiconductor laser oscillation, which
is dependent on temperature, becomes scattered.
In order to overcome the problem arising from the temperature
decrease, especially in the peripheral part of susceptor 1, heater
102 contained in the prior art apparatus should have a structure to
generate more heat from its peripheral part than the inside part.
To change the amount of heat generation, the cross-sectional area
of carbon heater 102 should be changed. Accordingly, the
cross-sectional area of heater 102 should be very small in the
peripheral part so as to increase the heat generation, as shown in
FIG. 8c. In this case, however, the mechanical strength of this
heater decreases.
As explained above, the prior art vapor growth apparatus has the
following disadvantages:
(1) the temperature of the peripheral part of the susceptor largely
decreases, and thus, the characteristics (including the wavelength
distribution of semiconductor laser oscillation) of individual
products made of wafers become inhomogeneous;
(2) if the cross-sectional area of the heater is set to be small
especially in the peripheral part so as to solve problem (1), the
heat generation in this part increases, but the mechanical strength
of the whole heater decreases.
SUMMARY OF THE INVENTION
This invention has been made to overcome the above mentioned
problems of the prior art apparatus.
Therefore, one objective of the present invention is to provide a
vapor growth apparatus for semiconductor devices which is capable
of unifying the temperature distribution of a susceptor without
losing the mechanical strength of a heater.
Another objective of the present invention is to provide a vapor
growth apparatus using a water cooled reaction tube of the vertical
type which can realize the uniform distribution of temperature in a
susceptor without loosing the mechanical strength of a heater.
Still another objective of the present invention is to provide a
vapor growth apparatus which is capable of obtaining many
semiconductor devices, having the same or almost the same
characteristics, at one fabrication process, by controlling the
temperature distribution of a susceptor to be uniform, as far as
possible. With such characteristics, for example, the oscillating
wave length of semiconductor lasers is contained.
The first feature of the present invention is to provide a vapor
growth apparatus for semiconductor devices which is comprised of
the following as shown in FIG. 1: a susceptor 1 which rotates in a
water cooled reaction room while holding semiconductor substrates
21 thereon; and a heater 2 for heating said susceptor 1; wherein
said heater 2 is comprised of inner and peripheral heaters 3 and 4,
which are electrically connected in parallel with each other.
The second feature of the present invention is to provide the vapor
growth apparatus having the first feature, wherein the temperature
of said peripheral heater 4 rises higher than that of inner heater
3.
According to the first and second features of this invention, a
plurality of semiconductor substrates (wafer) 21 are placed on
susceptor 1 which rotates in the water cooled reaction tube of the
vertical type, in order to carry out a vapor deposition. Heater 2
for heating susceptor 1 is, for example, in the form of a rectangle
as shown in FIG. 2 and is divided into inner heater 3 and
peripheral heater 4, which are electrically connected in parallel
with each other and integrated into one structure. The temperature
of peripheral heater 4 is controlled to be higher than that of
inner heater 3 by one temperature controller (not shown).
As mentioned above, heater 2 of this invention is comprised of
inner heater 2 and peripheral heater 3, which are connected in
parallel with each other. Therefore, the lower the resistor value
of peripheral heater 4 is, the more current flows through heater 4,
thus increasing the amount of heat generation in heater 4.
Accordingly, the cross-sectional area of peripheral heater 4 can be
set larger than that of inner heater 3, in contrast to the prior
art heater. Thus, the apparatus of this invention can make the
temperature distribution of susceptor 1 uniform without losing the
mechanical strength of heater 2. The apparatus of this invention
can, therefore, grow many semiconductor devices whose wafer
characteristics, such as the wave length distribution of laser
oscillation, are homogeneous.
These and other objectives, features, and advantages of the present
invention will be more apparent from the following detailed
description of preferred embodiments in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view showing the susceptor part of a
vapor growth apparatus according to one embodiment of this
invention;
FIG. 2a is a plan view of the heater which is contained in the
vapor growth apparatus shown in FIG. 1;
FIG. 2b is a cross-sectional view of the heater shown in FIG.
1;
FIG. 2c is a view showing the equivalent circuit for the heater
shown in FIG. 1;
FIG. 3a is a side view of the inner heater which is a part of
heater shown in FIGS. 2a, 2b, and 2c;
FIG. 3b is a plan view of the inner heater shown in FIG. 3a;
FIG. 3c is a cross-sectional view of the inner heater shown in
FIGS. 3a and 3b;
FIG. 4a is a side view of the peripheral heater which makes up the
heater shown in FIGS. 2a, 2b and 2c with said inner heater shown in
FIGS. 3a, 3b, and 3c;
FIG. 4b is a plan view of the peripheral heater shown in FIG.
4a;
FIG. 4c is a cross-sectional view of the peripheral heater shown in
FIGS. 4a and 4b;
FIG. 5 is a view showing the relation between the oscillating wave
lengths of semiconductor lasers and their distances from the center
of the susceptor;
FIG. 6a is a cross-sectional view of the vapor growth apparatus
having a water cooled reaction tube of the vertical type;
FIG. 6b is a plan view of the susceptor which holds semiconductor
substrates thereon in the vapor growth apparatus shown in FIG.
6a;
FIG. 7 is a cross-sectional view of the vapor growth apparatus
according to one prior art of the present invention;
FIG. 8a is a side view of an integral heater which is used in the
vapor growth apparatus of the prior art;
FIG. 8b is a plan view of the integral heater shown in FIG. 8a;
and
FIG. 8c is a cross-sectional view of the integral heater shown in
FIGS. 8a and 8b.
DETAILED DESCRIPTION OF EMBODIMENTS
In FIG. 1, the cross-sectional view of the susceptor part contained
in a vapor growth apparatus is shown according to one embodiment of
the present invention. In FIGS. 1 and 7, the same numbers show the
same or the similar structure elements with each other. In the same
manner as the prior art, the vapor growth apparatus of this
embodiment is used in the water cooled reaction tube of the
vertical type, the tube which has the cross-sectional structure
shown in FIG. 6.
As shown in FIG. 1, the vapor growth apparatus of this embodiment
is mainly comprised of the following: a susceptor 1 which rotates
in a water cooled reaction room with holding semiconductor
substrates thereon; a carbon heater 2 for heating susceptor 1; a
pair of thermocouples 9 for detecting the real temperature of
susceptor 1; and a susceptor receiver 11.
In FIGS. 2a, 2b, and 2c, the plan view, the cross-sectional view,
and the equivalent circuit view of heater 2 are shown. As shown in
these figures, heater 2 is divided into two parts, that is, inner
heater 3 and peripheral heater 4. These heaters 3 and 4 are
electrically connected in parallel and integrated into one
structure.
FIGS. 3a, 3b, and 3c show the side, plan, and cross-sectional views
of inner heater 3. As shown in these figures, inner heater 3 is
comprised of a carbon heater having a thickness h1 of 3 mm. The the
cross-sectional size of inner heater 3 is 2 mm.times.3 mm.
FIGS. 4a, 4b, and 4c are the side, plan, and cross-sectional views
of peripheral heater 4. The thickness h2 of peripheral heater 4 is
5 mm (h2>h1). This heater 4 is comprised of an outer circle 4c
and inner semi-circles 4a and 4b which are separated at the central
part. Connecting blocks 5a and 5b are fixed at each end of inner
semi-circles, as shown in the figures. Also, these outer circle 4c
and inner semi-circles 4a and 4b are connected with each other so
as to compose a series-parallel circuit. In other words, the whole
of peripheral heater 4 makes up a series-parallel circuit as shown
in FIG. 2c. In this figure, resisters R2 and R3 are from outer
circle 4c, resister R1 is from inner semi-circle 4a, and register
R4 is from inner semi-circle 4b. In addition, resister R5 is from
inner heater 3.
As mentioned above, heater 2 of this embodiment is comprised of
inner heater 3 and peripheral heater 4, which are connected in
parallel with each other. Therefore, the lower the resistance value
of peripheral heater 4 is, the more current flows through heater 4.
As a result, the amount of heat generation becomes large in heater
4. In this embodiment, in order to increase the generation of heat
further, the inner circle is divided into semi-circles 4a and 4b as
mentioned above, and a series-parallel circuit is formed with
registers R1, R2, R3, and R4. In this embodiment, therefore, the
cross-sectional area of heater 4 is made larger than that of heater
3, in order to decrease the resistance value of heater 4.
In addition, as shown in FIGS. 1 and 2, inner heater 3 is installed
at intermediate panels 7a and 7b through connecting blocks 6a and
6b, respectively. Similarly, peripheral heater 4 is installed at
intermediate panels 7a and 7b through connecting blocks 5a and 5b,
respectively. These intermediate panels 7a and 7b are then
connected with current supply terminals 8a and 8b.
The temperature control of heater 2 is carried out by one
temperature controller (not shown). A pair of thermocouples 9,
which is contained in susceptor 1 without touching the inner
surface, detects the real temperature of susceptor 1, and then, the
controller works to keep the susceptor temperature at a
predetermined value (about 800.degree. C.).
Peripheral heater 4 is designed to generate more heat than inner
heater 3. Therefore, the temperature of peripheral heater 4 is
controlled to be higher than that of inner heater 3.
In FIG. 5, the experimental result is shown for the relation
between the oscillating wave lengths .lambda. of semiconductor
lasers and distances R from the center of susceptor 1. These
semiconductor lasers are fabricated from semiconductor substrates
obtained with the vapor growth apparatus of this embodiment and the
prior art. As is evident from the figure values .lambda. of the
semiconductor lasers, which are fabricated using prior art heater
102, have a dispersion within 4 nm. On the other hand, values
.lambda. of the semiconductor lasers which are fabricated using
heater 2 of this embodiment, have a dispersion within 2 nm, which
is half of the prior art value.
As described above, this embodiment has the following
advantages:
(1) the temperature distribution of susceptor 1 has become uniform
in this embodiment, thus decreasing the amount of characteristic
dispersion (in oscillating wave length, etc. ) among lasers made by
the apparatus of this invention, such as .+-.1.0 nm, and so,
greatly improving the production yield of the devices;
(2) heater 2 is made thicker than that of the prior art and is
supported by four points, so that it is easy to handle without
damaging;
(3) peripheral heater 4 and inner heater 3 are integrated into one
structure by means of electric wirings, so that these heaters are
controlled to maintain uniform temperature by one temperature
controller of the conventional type; and
(4) the characteristics of wafers, which have been placed on the
peripheral part of susceptor 1 during a vapor growth process, have
been improved, thus increasing the number of good quality pellets
which are obtained from the wafers 21.
In summary, according to the present invention, the heater for
heating a susceptor is divided into two parts, such as an inner
heater and a peripheral heater. These two heaters are electrically
connected in parallel with each other so as to integrate them into
one structure. Also, these heaters are so controlled that the
temperature of the peripheral heater becomes higher than that of
the inner heater. Thus, this invention can have a heater which is
thicker than that of the prior art apparatus. As a result, this
heater can realize uniform temperature distribution on the
susceptor without losing its mechanical strength. As a result, this
invention provides a vapor growth apparatus which is capable of
fabricating many semiconductor devices having uniform
characteristics (the wave length distribution of oscillation,
etc.).
* * * * *